Power bank is a portable device that can be precharged and then charges other electrical devices like cell phones, pads and so on. A power bank normally comprises a battery and a control circuit thereof. FIG. 1 shows a block diagram of a prior art power bank 10. The power bank 10 comprises a charge circuit 101, a battery 102, a switch circuit 103, a select circuit 104 and a USB interface 105. In real application, when the power bank 10 is plugged, i.e., a power source Vsource is provided to the input terminal of the power bank 10, the battery 102 is charged by the power source Vsource via the charge circuit 101 while a load of the power bank 10 is powered by the power source Vsource via the select circuit 104 and the USB interface 105; when the power bank 10 is unplugged, i.e., the input terminal of the power bank 10 is disconnected from the power source Vsource, the load of the power bank 10 is powered by the battery 102 via the switch circuit 103, the select circuit 104 and the USB interface 105. The USB interface is configured to provide over voltage/current protection.
As shown in FIG. 1, the prior art power bank 10 comprises the battery 102, the charge circuit 101, the switch circuit 103, the select 104 and the USB interface 105 and so on. The system is complicated and the cost is high.
The present invention pertains to provide a power bank with simpler structure and lower cost.